Organic light emitting diodes (OLED) devices are becoming an increasingly important category of thin film organic semiconductor devices. Generally speaking, an OLED device includes an anode, an organic light emitting layer, and a cathode, wherein the organic light emitting layer includes a host material and a guest material. An OLED device operates by applying an external electric field, wherein electrons enter from the cathode and holes enter from the anode, of the OLED device. When the electrons and the holes meet after they travel through the electron transport layer and the hole transport layer, respectively, energy will be generated in the form of light (luminescence). This is a short-hand description of the organic light emitting phenomenon.
The OLED device, having characteristics such as free viewing angle, simple fabrication process, low production cost, fast response, wide operation temperature range, and full color display, etc., is expected to become the mainstream of new flat-panel displays.